You don't state your platform so ignore the bits that don't apply.

If these are form letters then you should consider generating a data file and using a word processor to perform mail merge for you. On Windoze OLE automation could be used to achieve this with minimal intervention. In Unix land a few well place system() calls might do the trick for you.

Alternatively, on Windoze, the entire document could be authored by OLE automation.

If you use the txt2pdf approach outlined above, perhaps one of the Text::Template style modules could be of assistance to get the bulk of the content sorted.